Treatment of coal-tar or its products for the removal of the properties therein tending to induce pitch-cancer.



Y H. w; ROBINSON. TREATMENT OF GOAL TAR OR ITS PRODUOTS FOR THE REMOVAL.OF THE PROPERTIES THEREIN PENDING TO INDUCE PITCH CANCER.

APPLICATION FILED FEB.11. 1914. I 1,1 14,045,. Patented Oct. 20, 1914.

UNITED STATES PATENT OFFICE.

HERBERT W. ROBINSON, OF SEDGLEY, ENGLAND.

TREATMENT OF COAL-TAR OR ITS PRODUCTS FOR THE REMOVAL OF THE PROPERTIESTEEREIN TENDINGTO INDUCE PITCH-CANCER.

Specification of Letters Patent.

Patented Oct. 20, 1914.

Application filed February 11, 1914. Serial N 0. 817,992.

Ta all whom it may concern Be it known that I, HERBERT WILLIAM ROBINSON,a subject of the King of Great Britain, and resident of Turls HillHouse, Sedgley, in the county of Stafford, England, have inventedcertain new and useful Improvements Relating to the Treatment ofCoal-Tar or Its Products forthe Removal of the Properties ThereinTending to Induce Pitch-Cancer, of which the following is aspecification. 7

Recent experiments-have been directed to the problem of ascertainingthecauses of cancer among workers in the industries producing andusing'pitch, and particularly in the manufacture of briquets wherein thepitch is employed as a binding agent for the coal dust. A recentpublication on this subject T he Problem of the Gas lVOrZcs PitchIndustries and Cancer issued under the auspices of the John HowardMcFadden researches (John Murray, Albemarle Street,

London, W. 1912) gives particulars of researches showing what resultshave been ob-I tained in experiments withsamples of'pitch and oilsobtained from coal tar; these experiments showedthat cancer would onlybe, induced when two diiterent classes, of sub;

stances were present, these being known under the-names of auxetlcsandkinetics respectively. Either of thesealone will not induce cancer, butwhen .both. are present cancer may be induced in workers who areconstantly working in the presence of dust containing the substances.The auxetics are certain agents present in dead matter, and areexc'iters of reproduction which stimulate cell-multiplication; amongthem may be mentioned creatin, xanthin (which contain the amidingrouping N-Q-N) methylamin (a primary amin) leucin and tyrosin(amino-acids). The kinetics are alkaloids which excite amoeboidmovements in the blood cells. Most alkaloids have this property.

Various ways were suggested of treating either the pitch or the tar inorder to remove from it either the auxetics or' the kinetics, and so torender it 1nnocuous in so far as the inducing of pitch cancer wasconcerned. It was suggested for instance that the desired result couldbe obtained by mixing a considerable amount of water with the tar whenthe water would dissolve out some of the constituents of the tar. Theaqueous solution was then to be separated from the tar by centrifugalaction or, otherwise. Experiments onthe resulting pitch and oils showedthat the kinetics could be removed 1n this way, and usually also theauxetics.

Now this process is not a practicable one, for

the present at any rate, from the point of view of the tar distiller.The expense is too great and valuable constituents of the tar aredissolved out by the water. I have therefore made some experiments withthe opject of ascertaining whether the addition 0 some chemicalsubstance to the-tar would produce the desired result at a comparetivelysmall expense, and without deleteriously affecting the value ofthe tarand of the products obtained therefrom. In so far as these experimentshave been carried u to thepresent, it has been found that an a dition ofeven small quantities of formaldehyde to the'tar at a convenientstagejin the distillation process, Iproduces at'least beneficialresults, the pitch obtained being free from auxetics, or containing onlysmall traces so that it would be com aratively harmless in so far as therisk 0' inducing cancer is concerned. The action of the formaldehyde isdoubtless due to its property of condensln'g organic nitrogen compounds,these being the compounds in the tar which by theresearch above referredto, are shown to'have auxetic properties.

In place of formaldehyde, para-formalde-' hyde, or otheraldehydes maybeused, as-it 18 found that the action in question is due to the-presenceof an aldehyde, andpraetically all aldehydes act, to some extent atleast, to get rid of auxetics. 'For example, acetic aldehyde may beused, or other aldehydes of the -fatty,group. The amount of the aldehydeadded and thestage in the process at which .it is added, will varyaccording to particular requirements and t0 the condition of the tar orpitch to be treated. It is not essential for most purposes to add thealdehyde in a pure form, and substances containing a suitable aldehydeor ca able of yielding an aldehyde during the su' sequent treatment oftheproduct, may be added to the tar of pitch. For example, sugardecomposes at a temperature below 250 C., with the formation ofvformaldehyde, and for somepurposes it may be cheaper or better to addsugar or the like 'to the product before or during the heating processin order to insure the presence of suflicient aldehyde to render theresulting pitch substantially free from auxetics.

When formaldehyde is to be added to the tar during the distillation, itis generally most convenient to efiect the distillation in the ordinaryWay until the carbolic acid and the earlier creosote fractions have beentaken off. When the temperature of the residue in the still reachesabout 250 to 270 (1., the distillation of further fractions consistingof heavy oils and so forth, is assisted by a current of steam introducedfor example through a perforated pipe in the still, and the formaldehydemay be introduced conveniently with this steam. I Alternatively, thetemperature of the material in the still may be reduced if necessary,and the formaldehyde or a substance capable of yielding a suitablealdehyde may be simply added before heating further to continue thedistillation. When the formaldehyde .is-

added with steam, the means for effecting the addition may be as shownin the accompanying drawing.

In this, Figure 1 shows a portion of the apparatus, and Figs. 2 and 3are detail views of a mixing jet used therein.

The steam is introduced into the still a (only part of which is shown)through a pipe I) from a boiler capable of supplying steam at therequired pressure. Commercial formalin is pumped through apipe d intostorage vessels 0 under a suitable air pressure, such as 20 to 30 poundsper square inch, and is supplied from these vessels as required throughcocks h and a pipe 0 to a jet for mixing it with the steam. A suitableform of jet is shown in Fig. 2 in elevation, partly in section, and inFig. 3 in plan. The pipe e terminates in a fitting at the top of thedevice and communicates with a jet 9 in a glass sight tube f. The lowerend of this tube communicates with the steam pipe b near to its point ofentry into the still a.

,With this construction, the feed of the formalin can be observed andthe jet can be removed and replaced easily if it becomes choked, whilethe feed of the formalin can be regulated by the cocks h as required.The regulation can be effected also by varying the pressure in thevessels 0, the size of the orifice of the nozzle g, the strength of thesolution, or by any combination 'of these means. In the case ofintermittent stills which are com letely emptied after each distillationof a c large of tar, it has been found convenient to introduce abouttwo-thirds of the total charge of formalin for each charge of tar,during the distillation as set forth above, and to add the remaining0ne-third after the withdrawal of the fire and while the Pitch residueis cooling in the still. About one anda half gallons of commercialformalin (40% solution of formaldehyde) have been used in successfulexperiments for a charge of 2,000 gallons of tar, but the quantity canbe varied to any extent according to the condition of the tar and theresults shown by experiment. The object is to eliminate the auxetics asfar as possible from the product, and to do this with the leastexpenditure of formalin or its equivalent.

.In the case of continuous stills, the formalin is introduced into thecompartments of the still where the heavy oil fractions are i beingdistilled'at temperatures above 250 0., and if jets are used as abovedescribed, the feed of formalin may be continuous in these compartments.The pitch drawn oft from the last compartment will be found to besubstantially free from auxetics, so that it would have little or notendency to induce cancer among operatives working with it.

The invention is not limited to the particular ways of adding theformaldehyde or its equivalent as set forth above, but any suitablemethod may be adopted of adding it at any convenient stage in thedistillation or to the pitch residue after the completion ofthedistillation.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:-

1. A process for treating tar or pitch with the object of removingtherefrom the properties tending to induce pitch cancer, the processconsisting in mixing with the tar or pitch less than 1% of a substanceyielding an aldehyde.

2. A process for treating tar or pitch with the object of removingtherefrom the properties tending to induce pitch cancer, the processconsisting in mixing with the tar or pitch less than 1% of a substancecontaining and yielding an aldehyde.

3. A process for treating tar or pitch with the object of removingtherefrom the properties tending to induce pitch cancer, consisting inadding less than 1% of an aldehyde to the tar or pitch before thecompletion of the distillation.

4. A process for treating tar or pitch with the object of removingtherefrom the propertiestending to induce pitch cancer, consisting inadding less than 1% of formalin to the tar .or pitch before thecompletion of the distillation.

5. A process for treating tar or pitch with the object of removingtherefrom the properties tending to induce pitch cancer, consisting inadding less than 1% of a substance yielding an aldehyde to the tarduring the distillation thereof at a stage after the separation of thecarbolic acid fraction and before the separation of the heavy oilfraction.

6. A process for treating tar or pitch with the object of removingtherefrom the properties tending to induce pitch cancer, consisting inadding less than 1% of a substance yielding an aldehyde to the tarduring the distillation thereof at a stage after the separation of thecarbolic acid fraction vand before the separation of the heavy oilfraction, and adding to the residue'a further quantity of said substanceafter the completion of the distillation.

' 7. A'process for treating tar or pitch with the object of removingtherefrom the properties tending to induce pitch cancer, consisting inmixing a small amount of formalin with steam and spraying the mixtureinto thedistillation still after the carbolicacid fraction has beenseparated and before the heavy oil fraction is separated.

'8. A process for treating tar or pitch with the object of removingtherefrom the properties tending to induce pitch cancer,'consisting inspraying a small amount of formalin under pressure into steam, andsupplying the mixture of steam and formalin into the presence of twosubscribing witnesses.

- HERBERT W. ROBINSON.

Witnesses:

HUBERT A. GILL, H. W. BLAKE.

